Malolactic fermentation promoters obtained from post-distillation wine lees using natural deep eutectic solvents

Abstract

Despite being the second winemaking by-product in terms of volume, wine lees remains mostly undervalued. This is especially true after distillation, when the removal of ethanol results in an unstable product difficult to transport or valorize, leaving distilleries in charge for its disposal. This study aims to propose a sustainable strategy for the stabilization and valorization of post-distillation wine lees (PDWL) as a source of high-value enological additives. PDWL from a local distillery were dried through a thermal treatment (135 °C to 90 °C, 6 h) that reduced moisture to 7.5 %, yielding a stable powder containing exhausted yeasts and wine sediments. The powder was extracted using three food-grade Natural Deep Eutectic Solvents (NADES) formulations (betaine mixed with citric, malic, or lactic acid) with a pH 3.4 McIlvaine buffer (MC) taken as a benchmark solvent. Extracts were combined with autoclave treatment (121 °C, 20 min) and ethanol precipitation to recover and concentrate proteins and polysaccharides. Although the use of NADES did not lead to an improvement of the extraction yield, citric acid/betaine and malic acid/betaine formulations allowed to obtain extracts with a higher polysaccharide content (39.2–45.4 %) compared to MC (25.2 %). The higher glucose-to-mannose ratio in these former samples suggests a higher amount of yeast ꞵ-glucans; conversely, yeast mannoproteins appeared to be more concentrated in both the lactic acid/betaine NADES and MC. The extracts’ impact on malolactic fermentation (MLF) was evaluated in model wine. Two O. oeni strains were inoculated at 1×10⁶ cells/mL and monitored for 144 h at 25 °C in the presence of the four extracts (0.4 and 1.0 g/L). Almost all trials significantly enhanced MLF speed in a dose dependent manner, enabling complete conversion of 2 g/L malic acid to lactic acid within 30–50 h. An increase in growth rate and population size was observed, rising from 1.68 × 10⁷ cells/mL (control) up to 2.33 × 10⁸ cells/mL. These findings suggest that PDWL extracts can enhance the tolerance of O. oeni strains to the stressful conditions of synthetic wine indicating their potential application as functional aids in winemaking.

References

De Iseppi, A.; Lomolino, G.; Marangon, M.; Curioni, A. (2020). Current and Future Strategies for Wine Yeast Lees Valorization. Food Res. Int., 137, 109352.

De Iseppi, A.; Marangon, M.; Curioni, A.; Perbellini, A.; Zanchin, A.; Guerrini, L. (2025). Recovery of Valuable Compounds from Distillery Vinasse: Trials for Plant Scale-Up. Appl. Sci., 15(18), 10192.

Teslić, N.; Curioni, A.; Marangon, M.; Stupar, A.; Lomolino, G.; Jones-Moore, H.; De Iseppi, A. (2025). Green Extraction of Glycoproteins and Polysaccharides from Wine Lees Using Natural Deep Eutectic Solvents. Food Chem., 493, 145742.